The present invention relates to a compliant tape guide for use with a data storage tape cartridge. More particularly, it relates to a compliant tape guide having a compliant member optimized for planar stiffness.
Data storage tape cartridges have been used for decades in the computer, audio and video fields. While other forms of media storage, such as diskettes are also available, the data storage tape cartridge continues to be an extremely popular form of recording large volumes of information for subsequent retrieval and use.
One type of data storage tape cartridge generally consists of an outer shell or housing maintaining at least one tape reel, a length of magnetic storage tape, and at least one tape guide. The storage tape is wrapped about and extends from the tape reel. The tape guide, in turn, articulates the storage tape through a defined tape path. In this regard, the tape path typically extends from the tape reel across a window portion (or read/write zone) of the housing. A door is normally associated with the window to provide selective access to the storage tape. During use, the data storage tape cartridge is inserted into a tape drive. The door is maneuvered into an open position and a transducer, such as a magnetic read/write head, engages the storage tape via the window. To ensure consistent, accurate engagement by the read/write head, the storage tape must be precisely positioned adjacent the window.
One common form of the data storage tape cartridge includes two tape reels. The storage tape extends between the two tape reels along a tape path defined by the tape guide. A driving system associated with the tape drive engages and directs movement of the tape reels to direct a desired portion of the storage tape to the cartridge window. Alternatively, the data storage tape cartridge may not have a tape guide. With this configuration, the tape drive itself will include a tape guide for directing the storage tape through a desired path.
With the two-reel design, the tape guide serves to define a tape path passing through the cartridge window. In this regard, the tape guide positions the storage tape within the cartridge window so as to be received by the read/write head. Any slight deviation from the desired planar positioning of the storage tape may result in reading/writing errors. If the storage tape is slightly above or below an expected location, upon insertion into the tape drive the read/write head will experience difficulties in finding a desired track on the storage tape. Similar problems occur if the tape path generates an angular orientation of the storage tape across the cartridge window. Additionally, the read/write head may encounter tracking problems whereby the head "loses" a desired track.
In light of the important role tape guides play in data storage tape cartridge performance, efforts have been made to improve upon tape guide design. One widely accepted form of a tape guide (or "compliant tape guide"), described in Erickson et al., U.S. Pat. No. 5,513,815, includes a top support plate, a bottom support plate, a bearing piece, a compliant member and a biasing member. The bearing piece extends between the top and bottom support plates to define a tape receiving surface generally perpendicular to the top and bottom support plates. The bearing piece is typically arcuate in form so as to direct the storage tape through a bend. Further, the bearing piece is normally disposed within an outer periphery of the top support plate and has a height slightly greater than a height of the storage tape. In this way, the non-magnetic side of the storage tape rides freely along the tape receiving surface of the bearing piece, while the outer periphery of the top support plate prevents an upper edge of the storage tape from disengaging the compliant tape guide. The compliant member, in turn, is configured to maintain a position (or height) of the storage tape relative to the top support plate.
More particularly, the compliant member includes a base, opposing legs and an edge receiving surface. The opposing legs extend from the base. The edge receiving surface is connected to the opposing legs opposite the base. The opposing legs allow the edge receiving surface to deflect relative to the base. With this in mind, the compliant member is connected to the bottom support plate such that the edge receiving surface extends beyond the tape receiving surface of the bearing piece. With this configuration, the edge receiving surface of the compliant member can engage a lower edge of the storage tape. Finally, the biasing member, which may include a plurality of spring-like fingers, is associated with the compliant member so as to bias or deflect the edge receiving surface toward the top support plate, in a plane substantially perpendicular to a plane of the storage tape.
During use, the compliant member guides the lower edge of the storage tape. This function is generally referred to as tape edge guiding. Notably, the compliant member is specifically designed to impart a known force on the lower edge of the storage tape. In other words, the opposing legs are configured to have a predetermined stiffness in a plane perpendicular to a plane of the top and bottom support plates (referred to as the "out-of-plane" stiffness). It is this stiffness that renders the overall tape guide "compliant." The edge receiving surface of the compliant member is "forced" into contact with the lower edge of the storage tape by the biasing member. However, the compliant member is not rigid so that the edge receiving surface can and will deflect slightly in response to movement of the storage tape. The predetermined out-of-plane stiffness provides a known force to the lower edge of the storage tape and therefore must be maintained within a relatively tight tolerance range so as to prevent damage to the storage tape.
The above-described compliant tape guide has proven to be highly successful in accurately directing and positioning storage tape within a data storage tape cartridge. The compliant member portion of the compliant tape guide enhances overall cartridge performance. Unfortunately, however, a potentially new problem may be created. While the out-of-plane stiffness of the compliant member is optimized to facilitate proper tape edge guiding, other cartridge vibrations may be generated. In particular, movement of the storage tape along the edge receiving surface of the compliant member, in conjunction with, and in response to, other internal vibrational sources, may cause the compliant member to vibrate in a plane substantially parallel to the plane of the top and bottom support plates (or substantially perpendicular to a plane of the storage tape). This is known as "in-plane" vibration. Under normal operating conditions, the in-plane vibration does not physically damage the storage tape or alter the tape path. However, where the vibration reaches a natural frequency of the compliant member, the compliant member may begin to resonate. This unexpected resonance of the compliant member may in turn be imparted onto the storage tape, resulting in excessive tape movement. When this occurs, the read/write head is unable to follow a servo signal track in the storage tape, causing a tape drive crash because the head is no longer able to follow the storage tape.
For example, it has been found that certain tape drives fail when an in-plane vibrational frequency of approximately 9 kHz on the compliant member was observed. It was determined that the standard design associated with the compliant member in question had an in-plane natural frequency of approximately 9 kHz. It is believed that the storage tape was maneuvered along and vibrated the edge receiving surface of the compliant member, and in response to other internal vibrational sources of the tape drive, the in-plane natural frequency of 9 kHz was reached, and the compliant member began to resonate, resulting in the above-described problem. Effectively then, at an in-plane vibrational frequency of 9 kHz, the compliant member portion of the compliant tape guide caused the tape drive to crash or fail by the head no longer being able to follow the storage tape.
Data storage tape cartridges are important tools used to maintain vast amounts of information. While the evolution of cartridge components, including storage tape and tape guides has greatly improved data storage tape cartridge capacity and performance, other unexpected problems have been identified. Therefore, a need exists for a compliant tape guide having a compliant member with a natural frequency different from an associated tape drive's operating frequency.